The present invention relates to a novel wire-driving device for a window regulator, and more particularly to a wire-driving device which can absorb automatically elongation generated in a wire transmitting power from the wire-driving device to a working device for raising and lowering of a window glass.
A wire comprising a strand of metal wire elements generally undergoes permanent elongation under a tension load. Permanent elongation does not permit the elongated wire to return to its initial length. The degree of the elongation is greater an initial stage of in use, but gradually becomes smaller, and continued tension on the wire finally results in almost non-elongation.
Elongation of the wire produces play between the wire-driving device and the working device in these functions, whereby the working device cannot be operates precisely. Thus, when the wire-driving device comes to stop, the working device still continues its function, and a window glass connected to the working device is moved in some degree without stopping in the desired position. Accordingly, it is unavoidable that the function of the working device is unstable.
Until now, in order to absorb elongation of the wire, a wire length-adjustment member comprising a bolt-nut system has been connected at an end or another suitable position of the wire in the window regulator. Thus, elongation of the wire has been removed by driving the bolt-nut. Also, in another method, a tension pulley is employed to remove elongation of the wire. However, according to these mechanisms for removing elongation of the wire, elongation of the wire must be adjusted in each time that elongation of the wire occurs. Also, performing the adjustment is very annoying, and often difficult.